The invention relates to light reflected, coded optical identification systems, specifically a target for reflecting light in such a way that a binary pattern of reflected light and nonreflected light can be interpreted by a sensing device as a binary code. The principal use contemplated for such device is to provide a system of optical character recognition in a hostile outdoor environment. Much interest has been focused on this general problem, particularly as it relates to systems having the ability to recognize and record, automatically, identifying numbers on railroad cars, trucks and ocean cargo containers.
Prior and current efforts in this field have depended on either surface reflection of light from plane surfaced targets coded with multi-colored striped or barred patterns, or on systems whereby light is projected through a target, and the code is read by a sensing device on the other side. There are disadvantages associated with both concepts. In the instance of colored panels it has been demonstrated through extensive experience that the patterns become coated with dirt, soot, etc. and become unreadable. In the second instance the need to have the illumination source and the sensing device on opposite sides of the target incurs serious mounting difficulties. This is especially true for ocean cargo containers which are essentially large boxes whereon the optical target must be mounted on some lateral surface of the container.
U.S. Pat. No. 3,255,177 is an early patent covering the color coded system mentioned above. The commercial form of this invention is marketed under the trade name of "KARTRAK" by the Servo Corporation of America, Hicksville, N.Y. Modifications of this system are disclosed in U.S. Pat. No. 4,002,889 assigned to the Servo Corporation.
In the second field of the invention cited above, U.S. Pat. No. 3,304,412 discloses a system wherein a light source mounted on the side of a rail track shines through a perforated coded target attached to the rail car journal box to be read by a track side sensing device.
Other patents relating to this general area are: U.S. Pat. Nos. 3,277,283 and 3,316,392.
As will be seen the present invention is conceived to overcome these shortcomings.